The arrest of a Mississippi Klansman reopens one of the South's most infamous unresolved murder cases

Edgar Ray Killen called himself a Baptist minister, but he worshipped in the church of the Ku Klux Klan. So when Killen, a native of Philadelphia, Miss., became his local Klan's Kleagle (a top commander) in the 1960s, he finally felt ordained with genuine power--and he allegedly used it to recruit and organize more than a dozen Klansmen in the 1964 murder of three civil rights workers.

The deaths of James Chaney, 21, a black Mississippian, and two white New Yorkers, Michael Schwerner, 24, and Andrew Goodman, 20, came to symbolize white resistance to the "Freedom Summer" campaign to register black...